Protective clothing of many types is now well known of many and varied uses in protecting people from fire and harmful substances, such as suits for industrial workers, flame and fire resistant suits for fireman, forest fire fighters, race car drivers and airplane pilots, and suits for use by military personnel. Garments include not only complete, hermetic suits, but also individual garments such as trousers, jackets, gloves, boots, hats, head coverings, masks, etc.
Regulations restricting exposure to hazardous environments of various kinds, such as the Occupational Safety and Healt Act, make it increasingly necessary to have better and more effective kinds of protective garments.
Such garments presently available are almost invariably of thick construction and heavy in weight, and are often fabricated at least in part from materials impermeably to water or water vapor, such as natural and synethetic rubbers and elastomers, chlorinated rubbers, etc.
The use of aluminized film coated fabrics (AFCF) for fire proximity suits for firefighters depends on the ability of the surface of the resulting garment to reflect theradiant heat emitted from the fire. (About 75% of the heat or energy emitted from a flame source is radiant or infra red energy). The use of AFCF suits is highly effective, but the aluminum coating is soft and is abraded very readily, causing loss of protection in the abraded area, i.e., hot spots. There has been, and continues to be, a need for a suitable abrasion resistant coating for the AFCF suits that will not decrease the reflecting performance of the aluminum film. Such a film would increase the performance life of the suits and significantly reduce the effective costs of using these fire protective suits.
Two additional concerns besides the critical one of improving the abrasion resistance of the aluminum film are (1) the need to raise the service temperature of the substrate film from 400.degree. F. to about 500.degree. F. and (2) to improve the flexibility of the suit. Firefighters will continue to work as close to fires as they can and will be subject to direct flame excursions. The film will eventually be heated beyond its softening/melting point and the smooth aluminum surface is lost. The suit will rapidly become ineffective, endangering the firefighter. A higher service temperature film can provide a greater margin of safety for the user.
The stiffness and weight of the aluminized film plus the fabric make a fire-proximity suit physically tiring to wear. There is a need to improve the flexibility and lighten the weight of this suit without affecting its protective performance.
One means of coating surfaces with a metallic substance comprises sputter deposition. Sputter deposition results from the ionic bombardment of source target materials (metals) and subsequent ejection of atoms from these materials (metals) to form thin films on substrate surfaces. The ejected target atoms bombard the substrate surfaces at such high velocities that the resulting film is an atomic mixture of atoms from the target and substrate materials. The metal film will not usually separate from the substrate by flexing, heat, peeling or abrasion as might be expected of sprayed, electroplated or vapor deposited coatings.
Other plastic films also being coated with aluminum and sold commercially include Kapton, Surlyn, polystyrene, polypropylene and the like.
Other methods of aluminizing used in other applications include (1) the fabric being metallized by treating it with a metal pigmented coating, (2) thin metal film foil being laminated onto the fabric, and (3) transfer of the metal from a metallized film to a substrate (fabric) with a curable adhesive, and curing the adhesive. This technique is widely used for decorative applications in the metallized paper industry and has applications in the decorative fabric field. (The adhesive has to be acrylic for electron beam curing).
Most lamination processes are continuous "roll-to-roll" laminations with an adhesive followed by post curing and additional curing via a series of one or more sets of heated nip rolls. The actual lamination lines and the adhesives are considered proprietary. The adhesive systems utilized are usually fire resistant versions of polyurethanes, neoprene latexes, epoxies, polyimides and polyesters.
The fabrics currently used as the backing for AFCF are woven (plain weave, basket weave and 2.times.2 twill). These fabrics are predominantly Kevlar for the military with some Kevlar/PB1 (60/40).
In the specific application of reflective aluminized firefighter's coats, the aluminized Mylar film is laminated to strong, lightweight, fire resistant fabric. These coats function by reflecting about 90-92% of the spectral infra red (IR) light away from the body. In cases of petroleum fuel fires, about 75% of the heat is transferred by IR radiation to the firefighter. The aluminum film on the polyester (Mylar) is very flexible, but is very thin and prone to be abraded off or subject to delamination. The delamination is due to the absorption of the Mylar of water vapor or chemical solvents through the pin holes in the aluminum coating followed by loss of adhesion between the aluminum surface and the polyester film (Mylar). The aluminum is coated on both sides of the polyester film but as the outside coating is worn away, the IR energy passes through the layer of polyester film and is reflected back, passing through the film a second time. The film absorbs some of the IR energy and its temperature is raised. If the temperature of the polyester film exceeds 400.degree. F. by much, the film melts and fails and the coat develops a hot spot with significant heat passing into the nominal insulative clothing which was not designed for this extra heat and the firefighter must leave the area before receiving burns.
There has been a continuing search to find an abrasion resistant coating which can extend the life time of these garments by protecting the outer aluminum layer from abrasion and delamination. Up to now, no such coating has been found which (1) increases the abrasion resistance of the aluminum film significantly in very thin coatings, more than double; (2) adheres to the metal surface (actually the surface is a thin aluminum oxide film over the aluminum) very well through flexing and immersion in hot water, and (3) is relatively transparent to IR and does not reduce the reflectivity of the aluminum film by more than 2.5%.
Attempts have been made to provide the protective clothing with coatings that will resist abrasion. U.S. Pat. No. 4,284,682 to Factor, et al discloses a flexible, flame retardant, abrasion resisting coating which comprises thermoplastic polyurethane and flame retardant additives that are placed on a fabric substrate. However, the coating cannot be utilized on metallized surfaces because of delamination.
U.S. Pat. No. 4,371,585 to Memon, which is herein incorporated by reference, discloses silicone or siloxane-based abrasion resistant coatings which are placed on a polycarbonate substrate which does not crease and flex as a fabric structure. Moreover, conventional silicone and siloxane compositions are usually not suitable by themselves for coating metal surfaces.
It is therefore an object of the invention to provide an abrasion and fire resistant coating on a metallized substrate which will not crack or delaminate.
It is another object of the invention to provide a coating on metallized protective clothing and fabrics which is non-burning/charring and can be utilized at high temperatures.
It is a further object of the invention to provide a coating on metallized protective clothing, fabrics and other substrates which is transparent.
It is yet a further object of the invention to provide substrates having a first primer coating and a second abrasion-resistant coating.